Obstetric Outcomes by Hospital Volume of Operative Vaginal Delivery

Characterizing hospital-level factors associated with adverse outcomes following operative vaginal delivery (OVD) is crucial for optimizing obstetric care.

To assess the association between hospital OVD volume and adverse outcomes.

This was a retrospective cohort study of OVDs in California between 2008 and 2020. OVD was determined using birth certificate and International Classification of Diseases, Ninth Revision, Clinical Modification or International Statistical Classification of Diseases, Tenth Revision, Clinical Modification codes. This study used linked vital statistics and hospital discharge data from California. The study included singleton, nonanomalous, full-term deliveries with vertex presentation. Data analysis was performed between June 10 and October 23, 2024.

Hospital OVD volume was categorized by the proportion of OVDs performed among all deliveries, grouped into low (<5.2%), medium (5.2%-7.4%), and high (≥7.4%) volume.

Adverse outcomes for birthing individuals included obstetric anal sphincter injuries, cervical lacerations, and postpartum hemorrhage. Neonatal outcomes included shoulder dystocia, subgaleal hemorrhage, intracranial hemorrhage, facial nerve injury, and brachial plexus injury (BPI). χ2 and multivariable Poisson regression analyses were used to assess the association between hospital OVD volume and outcomes.

Among 306 818 OVDs (mean [SD] birthing parent's age, 28.5 [6.2] years; 155 157 patients with public insurance [50.6%]), hospitals with low OVD volume had an increased proportion of obstetric anal sphincter injury compared with hospitals with medium and high volumes (12.16% [7444 patients] vs 11.07% [10 709 patients] vs 9.45% [14 064 patients]). Hospitals with low volume also had a higher proportion of adverse neonatal outcomes, including shoulder dystocia (3.84% [2351 patients] vs 3.50% [3386 patients] vs 2.80% [4160 patients]), subgaleal hemorrhage (0.27% [165 patients] vs 0.18% [172 patients] vs 0.10% [144 patients]), and BPI (0.41% [251 patients] vs 0.30% [291 patients] vs 0.20% [301 patients]) compared with hospitals with medium and high volume. In multivariable analyses, low OVD volume remained associated with increased risk of obstetric anal sphincter injury (adjusted risk ratio [aRR], 1.36; 95% CI, 1.14-1.62), shoulder dystocia (aRR, 1.30; 95% CI, 1.10-1.52), subgaleal hemorrhage (aRR, 2.57; 95% CI, 1.55-4.24), and BPI (aRR, 1.73; 95% CI, 1.30-2.2.29) compared with hospitals with high OVD volume. After multivariable analysis, medium OVD volume remained associated with increased risk of subgaleal hemorrhage (aRR, 1.72; 95% CI, 1.04-2.86) and BPI (aRR, 1.35; 95% CI, 1.02-1.79) compared with high OVD volume.

This study found that undergoing OVD at hospitals with low OVD volume was associated with adverse perinatal outcomes compared with hospitals with medium and high OVD volumes. Further exploration of the reasons for these differences and prevention of these differences is needed to improve obstetric outcomes.